Absorption, distribution, metabolism, excretion (ADME) and Toxicokinetic (TK) studies of chemicals are necessary for the optimal design and interpretation of rodent toxicity and carcinogenicity studies. Studies are designed with the intent of enhancing our knowledge on structure-activity relationships that determine chemical toxicity and provide basic information to support more accurate extrapolation of laboratory data to assess human health risks. The mechanistic studies performed under this contract provide basic information related to toxic effects of chemicals in rodents thus aiding the extrapolation to humans.